Species richness influences wine ecosystem function through a dominant species

Increased species richness does not always cause increased ecosystem function. Instead, richness can influence individual species with positive or negative ecosystem effects. We investigated richness and function in fermenting wine, and found that richness indirectly affects ecosystem function by altering the ecological dominance of Saccharomyces cerevisiae. While S. cerevisiae generally dominates fermentations, it cannot dominate extremely species-rich communities, probably because antagonistic species prevent it from growing. It is also diluted from species-poor communities, allowing yeasts with lower functional impacts to dominate. We further investigated the impacts of S. cerevisiae and its competitors in high- and low-functioning wine communities, focusing on glucose consumption as an ecosystem function. S. cerevisiae is a keystone species because its presence converts low-functioning communities to communities with the same function as S. cerevisiae monocultures. Thus, even within the same ecosystem, species richness has both positive and negative effects on function

Fungal diversity during fermentation correlates with thiol concentrations in wine

Background and Aims: Agricultural products produced by the same genotypic clone often have different physical and sensorial properties, influencing their overall quality and economic value. Microbes play key roles throughout the production of these goods, affecting plant and fruit health and modifying plant materials to produce socially and economically important commodities. Following this idea, we investigated whether the fungal diversity in the pre-fermented grape juice, and also during fermentation, was correlated with the final concentration of three volatile thiols important to Sauvignon blanc aroma and flavour. Methods: we used metagenomics to quantify yeast populations and GC-MS to quantify thiols and analysed these using random forest statistical approaches. Results: The species of Saccharomyces yeast, the main driver of fermentation, was found to have a significant effect on the concentration of 4MMP in the final wine. Using next-generation sequencing technologies we also identified a number of non-Saccharomyces genera present early in the ferment that correlate with the thiol concentrations. Conclusion: These data suggest non-Saccharomyces fungi may be affecting the accumulation of odourless precursors in the grape itself via pathogenic effects during fruit ripening. Significance: This recapitulates the need for a better understanding of the interactions between microbial populations and agricultural products and has implications for the management of fungal diversity and disease in these systems

Efficient but occasionally imperfect vertical transmission of gut mutualistic protists in a wood‐feeding termite

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